In an electric or hybrid motor vehicle, one part of the electrical circuit is powered at a high voltage of the order of 400 volts, while the power supply for the control circuits generating and carrying the control signals is made with low voltage, of the order of 5 to 12 volts.
The part powered with high voltage generally comprises all of the functional power modules, such as the propulsion motor of the vehicle and the heater of the vehicle. The high voltage enables, for equal power, intensity, and therefore losses due to Joule effect, to be lowered. The part powered with low voltage for its part comprises in particular the control elements, such as a connection bus.
The two parts of the electrical circuit are separated by an isolation, called a galvanic barrier, allowing prevention of a discharge of high voltage into the low voltage part. Passages through the galvanic barrier are made by means of electrical transformers, located between the high and low voltage lines that are called upon to interact.
In order to control the functions of the circuit, the latter comprises a microcontroller, which controls the different functional modules of the circuit, according to instructions applied by the user via switching modules and/or signals emanating from sensors linked by the low voltage bus. In particular, it is impossible to make analog voltage or intensity measurements pass through the galvanic barrier without resorting to a costly converter.
Therefore, if the microcontroller is located on the low voltage side of the galvanic barrier, it will only be able to receive measurements concerning the high voltage functional modules of the circuit through interposed converters, which adversely affect precision and/or are costly.
If the microcontroller is located on the high voltage side of the galvanic barrier, it will be impossible for it to control the disabling of the device without implementing additional galvanically decoupled lines, controlling the elements forming the galvanic barrier is then particularly problematic.